RE: .25 Cal Nosler Accubond Load Data needed!!!
I developed some loads for this bullet in the .25-06 Ackley Improved, which is a caliber of similar performance to the .257 Weatherby. Using the same charges as the 117 gr. Sierra worked about pretty well for me. I hesitate to give you a specific maximum load, but I would use RL22 or H4831SC and start out where the book says to start with the 117 Sierra. You also might contact Nosler, either by phone or e-mail, for their suggested starting loads. Good luck. Roskoe.
PS - this bullet is turning out to be one of the best all around performers I have ever used at these velocities.